The present invention relates to a fuel injection valve used for an engine, a method of fuel injection to an engine, and an assembly method of the fuel injection valve.
For instance, a fuel injection valve which injects the fuel after heating the fuel injected from the fuel injection valve is disclosed in Japanese Patent Application Laid-Open No. 2000-230465 and Japanese Patent Application Laid-Open No. 2003-314402. The fuel injection valve described in Japanese Patent Application Laid-Open No. 2000-230465 forms a plurality of fuel passages in order to change the shape of spray, and heats the fuel which flows in the fuel passage selected from among a plurality of fuel passages with the heater. In the invention of Japanese Patent Application Laid-Open No. 2003-314402, heating wire has been wound around a movable needle valve.
However, the heater is arranged to contact the casing in the technology of Japanese Patent Application Laid-Open No. 2000-230465. Therefore, a part of heat from the heater is transferred to the casing when heating of the fuel is tried at the starting point of time, and the heating efficiency of the fuel is deteriorated. Therefore, the heating time becomes long and there is a possibility that the electric power consumption additionally increases, too.
Moreover, the passage is separated to a plurality of ones, and a heater is arranged in the passage selected from among them. Therefore, there is a passage where the heater is not provided for either. After all, only a part of the fuel to be injected is heated, and the atomization of the entire fuel to be injected might not be promoted.
By the way, it is more advantageous to promote the atomization of the fuel to burn the fuel easily as much as possible, in order to improve the starting characteristic of the engine and to decrease the harmful exhaust gas. In general, it is about 0.5 seconds and little time until the key is turned on when the engine is about to be started and the cranking is begun, and the injection of the fuel for the starting is begun. Ignitability can be improved when the atomization of the fuel is performed at that time and the emission of unburnt hydrocarbon (HC) can be decreased especially. Moreover, the electric power consumption of a starter is large at the cranking, and the power electric load to the battery is large during that time. Therefore, when the equipment by which the electric power is consumed is operated, making to the power saving is especially requested. Therefore, an electric heater which heats the fuel must increase efficiently the temperature of the fuel within a short time.
In Japanese Patent Application Laid-Open No. 2003-314402, the heating wire wound around the needle valve warms up the entire needle valve. As a result, the fuel in the entire surroundings of the long needle valve is heated. Therefore, an essential start ability might worsen, because power consumption increases, and an extra load not only is applied to the battery, but also the power supply to the starter decreases.